For most of his career, Christopher Hitchens, who has died of oesophageal cancer aged 62, was the left's biggest journalistic star, writing and broadcasting with wit, style and originality in a period when such qualities were in short supply among those of similar political persuasion. Nobody else spoke with such confidence and passion for what Americans called "liberalism" and Hitchens (regarding "liberal" as too "evasive") called "socialism".

His targets were the abusers of power, particularly Henry Kissinger (whom he tried to bring to trial for his role in bombing Cambodia and overthrowing the Allende regime in Chile) and Bill Clinton. He was unrelenting in his support for the Palestinian cause and his excoriation of America's projections of power in Asia and Latin America. He was a polemicist rather than an analyst or political thinker – his headteacher at the Leys school in Cambridge presciently forecast a future as a pamphleteer – and, like all the best polemicists, brought to his work outstanding skills of reporting and observation.

To these, he added wide reading, not always worn lightly, an extraordinary memory – he seemed, his friend Ian McEwan observed, to enjoy "instant neurological recall" of anything he had ever read or heard – and a vigorous, if sometimes pompous writing style, heavily laden with adjectives, elegantly looping sub-clauses and archaic phrases such as "allow me to inform you".

His socialism was always essentially internationalist, particularly since the British working classes responded sluggishly to literature he handed out at factory gates for the International Socialists, a Trotskyist group of which he was a member from 1966 to 1976. He had little interest in social or economic policy and, in later life, seemed somewhat bemused at questions about his three children being educated privately.

Hitchens travelled widely as a young man, often at his own expense, visiting, for example, Poland, Portugal, Czechoslovakia and Argentina at crucial moments in their anti-totalitarian struggles, offering fraternal solidarity and parcels of blue jeans. Later, he rarely wrote at length about any country without visiting it, sometimes at risk of arrest or physical attack. His loathing of tyranny was consistent: unlike many of the 1960s generation, he never harboured illusions about Mao or Castro. His concerns grew about the left's selective tolerance for totalitarian regimes – as early as 1983, he ruffled "comrades" by supporting Margaret Thatcher's war against General Leopoldo Galtieri's Argentina – but they did not initially threaten a rupture in his political loyalties.

After the terrorist attacks on New York and Washington in 2001, however, Hitchens announced he was no longer on the left – while denying he had become any kind of conservative – and "swore a sort of oath to remain coldly furious" until "fascism with an Islamic face" was "brought to a most strict and merciless account".

To the horror of former allies, he accepted invitations to the George W Bush White House; embraced the deputy defence secretary and Iraq war hawk Paul Wolfowitz as a friend ("they were finishing each other's sentences", was one account of an early meeting); and resigned from the Nation, America's foremost leftwing weekly. In 2007, after living in the US for more than 25 years, he took out American citizenship in a ceremony presided over by Bush's head of homeland security. Long friendships with the aristocracy of the Anglo-American left – Noam Chomsky, Tariq Ali, Alexander Cockburn, Edward Said – ended in harsh exchanges. Gore Vidal once named Hitchens as his inheritor or dauphin. The relevant quotation appeared on the dustjacket of Hitch-22, Hitchens's memoir published in 2010, but was overlain by a red cross with "no, CH" inscribed beside it.

Hitchens was born in Portsmouth to parents of humble origins who progressed to the fringes of what George Orwell (a Hitchens role-model) would have termed the lower-upper-middle-classes. His father was a naval commander of "flinty and adamant" Tory views who became a school bursar. Father and son were never close; nor were Christopher and his younger brother, Peter. The first love of Hitchens's life was his mother, "the cream in the coffee, the gin in the Campari". She insisted (at least according to Hitchens) he should go to boarding school because "if there is going to be an upper class in this country, then Christopher is going to be in it".

He was already a Labour supporter at school, organising the party's "campaign" in a mock election, and joining a CND march from Aldermaston. At Balliol College, Oxford, where he read philosophy, politics, and economics, he "rehearsed", as he put it, for 1968. But he led a curiously dualistic life. By day, "Chris" addressed car workers through a bullhorn on an upturned milk crate while by night "Christopher" wore a dinner jacket to address the Oxford Union or dine with the warden of All Souls. (He did not, in fact, like being called "Chris" – his mother would not, he explained, wish her firstborn to be addressed "as if he were a taxi-driver or pothole-filler" – and found "Hitch", which most friends used, more acceptable.) While not exactly a social climber, Hitchens wished to be on intimate terms with important people.

Equally dualistic was his sex life. He was almost expelled from school for homosexuality and later boasted that at Oxford he slept with two future (male) Tory cabinet ministers. But also at Oxford, he lost his virginity to a girl who had pictures of him plastered over her bedroom wall and he eventually became a dedicated heterosexual because, he said, his looks deteriorated to the point where no man would have him.

The "double life", as he called it, continued after he left university with a third-class degree – he was too busy with politics to bother much with studying – and found, partly through his Oxford friend James Fenton, a berth at the New Statesman. He supplemented his income by writing for several Fleet Street newspapers, but also contributed gratis to the Socialist Worker.

It was while working for the Statesman that he experienced a "howling, lacerating moment in my life": the death of his adored mother in Athens, apparently in a suicide pact with her lover, a lapsed priest. Only years later did he learn what she never told him or perhaps anyone else: that she came from a family of east European Jews. Though his brother – who first discovered their mother's origins – said this made them only one-32nd Jewish, Hitchens declared himself a Jew according to the custom of matrilineal descent.

Later in the 1970s, Hitchens became a familiar Fleet Street figure, disporting himself in bars and restaurants and settling into a literary set that included Fenton, Martin Amis, Julian Barnes, Clive James and others. It specialised in long lunches and what (to others) seemed puerile and frequently obscene word games. But he was hooked on America as a 21-year-old when he visited on a student visa and tried unsuccessfully to get a work permit. In October 1981, on a half-promise of work from the Nation, he left for the US. It was the making of his career: Americans have always had a weakness for plummy voiced, somewhat raffish Englishmen who pepper their writing and conversation with literary and historical allusions.

He became the Nation's Washington correspondent, contributing editor of Vanity Fair from 1982, literary essayist for Atlantic Monthly, a frequent contributor to the New York Review of Books and a talking head on innumerable cable TV shows. He authored 11 books, co-authored six more, and had five collections of essays published. The targets included Kissinger, Clinton and Mother Teresa ("a thieving fanatical Albanian dwarf"); his books on Orwell, Thomas Jefferson and Thomas Paine were more positive, and less widely noticed. His most successful book, which brought him international fame beyond what Susan Sontag called "the small world of those who till the field of ideas", was God Is Not Great, a mocking indictment of religion which put him alongside Richard Dawkins as a leading enemy of the devout.

Hitchens was also, to his great pleasure, a liberal studies professor at the New School in New York and, for a time, visiting professor at Berkeley in California, as well as a regular on the public lecture and debate circuit. Hitchens loved what he called "disputation" – there was little difference between his public and private speaking styles – and America, a more oral culture than Britain's, offered ample opportunity. When his final break with the left came, it seemed to some as though the pope had announced he was no longer a Catholic. His support for Bush's war in Iraq – which he never retracted – and his vote for the president in 2004, were even bigger shocks, and some suspected a psychological need, as the first male Hitchens never to wear uniform, to prove his manhood. But Hitchens, in many respects a traditionalist, was never a straightforward lefty. He abstained in the UK's 1979 election, admitting he secretly favoured Thatcher and hoped for an end to "mediocrity and torpor".

The Ayatollah Khomeini's fatwa, issued in 1989 against his friend Salman Rushdie, was, in Hitchens's mind, as important in exposing the left's "bad faith" as 9/11. He supported, albeit belatedly, the first Gulf war, demanded Nato intervention in Bosnia, and refused to sign petitions against sanctions on Saddam Hussein's Iraq. Hitchens, though, did not deny he had changed. He became, if truth be told, a bit of a blimp and ruefully remarked – with the quiet self-irony that often underlay his bombastic style – that he sometimes felt he should carry "some sort of rectal thermometer, with which to test the rate at which I am becoming an old fart".

But, he insisted, he wasn't making a complete about-turn. Though no longer a socialist, he was still a Marxist, and an admirer of Lenin, Trotsky and Che Guevera; capitalism, the transforming powers of which Marx recognised, had proved the more revolutionary economic system and, politically, the American revolution was the only one left in town. He remained committed to civil liberties. After voluntarily undergoing waterboarding, he denounced it as torture, and he was a plaintiff in a lawsuit against Bush's domestic spying programme. He never let up in his "cold, steady hatred … as sustaining to me as any love" of all religions.

Other things were unchanging. Hitchens's life was full of feuds with old friends. He broke with the Clinton aide Sidney Blumenthal who, before a congressional committee, denied spreading calumnies about Monica Lewinsky. Hitchens, earning himself the sobriquet "Snitchens", signed affidavits testifying that Blumenthal had, in his hearing, indeed smeared the president's lover. His rightwing brother, Peter, also a journalist, was put on non-speakers for several years after revealing a pro-red joke that Christopher once made in private. But his friendship with Amis never wavered. "Martin … means everything to me," he once said, while "more or less" acquitting himself of carnal desire. Amis, in turn, spoke of "a love whose month is ever May" and described his friend as a rhetorician of such distinction that "in debate, no matter what the motion, I would back him against Cicero, against Demosthenes".

Hitchens's love affairs with alcohol and tobacco were equally constant. He smoked heavily, even on public occasions and even on TV, long after the habit – for everyone else – became unacceptable. Despite reports in 2008 that he had given up, a reporter found him getting through two packets of cigarettes in a morning in May 2010. As for alcohol, he drank daily, on his own admission, enough "to kill or stun the average mule". Technically, he was probably an alcoholic but, he pointed out, he never missed deadlines or appointments. Regardless of condition, he wrote fast and fluently, if with erratic punctuation. Only rarely did alcohol make him a bore, blunt his wit or cloud his arguments. The journalist Lynn Barber rated him "one of the greatest conversationalists of our age". Inebriated or sober, he could charm almost anybody. He could also, with what the New Yorker's Ian Parker called "the sudden, cutthroat withdrawal of charm", wound deeply and unnecessarily.

In the summer of 2010, during a promotional tour for Hitch-22, he was diagnosed with terminal oesophageal cancer, a disease that had killed his father at a much more advanced age. He inhabited "Tumourville", as he called it, with rueful wit and little self-pity. "In whatever kind of a 'race' life may be," he wrote, "I have abruptly become a finalist." In the same Vanity Fair article, he observed that "I have been taunting the Reaper into taking a free scythe in my direction and have now succumbed to something so predictable and banal that it bores even me". But he never repented of his convivial lifestyle – on the contrary, he continued to take his beloved whisky, having received no medical instructions to the contrary – and nor did he turn his rhetorical skills to persuading others to eschew his example, confining himself, in a TV interview, to the observation that "if you can hold it down on the smokes and cocktails, you may be well advised to do so".

He continued, as well as giving valedictory newspaper and magazine interviews, to write, broadcast and participate in public debates with no discernible diminution of vigour or passion. He confronted the Catholic convert Tony Blair before an audience of 2,700 in Toronto and, by general consent, won with ease. He gave early notice that there would be no deathbed conversion to religion. If we ever heard of such a thing, he advised, we should attribute it to sickness, dementia or drugs. When believers prayed for him, he politely declared himself touched, but resolute in his atheism. He was as severe with the conventional cliches of terminal illness as he was, throughout his life, with any other form of convention.

"To the dumb question 'Why me?'," he wrote, "the cosmos barely bothers to return the reply, 'Why not?'" All the same, his many friends and admirers, who do not, as one of them put it, "relish a world without Hitchens", will be asking "why him?" today.

Hitchens was married, first, to Eleni Meleagrou, a Greek Cypriot, and then, after they divorced, to Carol Blue, an American screenwriter. Both survive him, as do one son and two daughters.

• Christopher Eric Hitchens, journalist, born 13 April 1949; died 15 December 2011